Pebble heat exchanger



2 SHEETS-SHEET 1 Oct. 21, 1952 Filed Oct. 11, 1948 INVENTOR.

L. J. WEBER BY ATTORNEYS Patented Oct. 21, 1952 PEBBLE HEAT EXCHANGER Louis J. Weber,- Bartlesville, Okla., assignor to PhillipsPetroleum Company, a corporation of Delaware Application October 11, 19.48,, Seri'aINo. 53,876

2. Gl'aims. 1

This invention relates to pebble heatiexchangers. In one of its more specific aspects itrelates to improved'pebble heater chambers. In another of its more specific aspects, it relates; to an improved method for operating pebbleyheater -chambers.

Thermal conversion processes carried on insocalled pebble heater apparatus utilize a flowing mass of pebbles which is heated to ahigh temperature in a first direct heat exchange Step and is then caused to contact gaseous materials furnishing heat thereto; in a second directheat exchange. The conventional pebble heater apparatus comprises two chambers which may be disposed in substantially vertical alignment. Solid heat exchange material, suchasrefractory pebbles, is ordinarily introduced into the-upper portion of afirst chamber andis allowed-todrop vertically'to a point at which a fluidbed of-such solid heat exchange material is iormed by such dropping pebbles. Thesolidheat exchange material flows downwardly through the pebble heater chamber in direct heat exchange with a, hot gaseous heat exchange material. li he solid heat exchangematerial is heated to a high temperature in such a heatexchange-and passes as a pebble stream into a second chamberin which the pebblesare caused tocontacta second gaseous materialin a second directheatexchange relation furnishing heat thereto.

The term pebbles asused herein: denotes any solid refractory material otflowable form, size and: strength which is suitable, to; carry. large amounts of heat from; the pebble heating chain? berto the gas heating chamber. Pebbles convene tionally used in such pebble heater apparatus-are substantially spherical in shape andare from about one-eighth inch toabout one inch. in diam.

eter. In high temperature processes the pebbles must be formed of. arefraetol'y materialtwhich will withstand temperatures at least as highas thehighest temperature attained in thepebble heaterchamber. I he pebbles must also becapable; of withstanding. any temperature changes ithin the apparatus. A refractory material, such asa metal, ceramic or other satisfactory materialimaybe utilized to form such pebbles. Suit.-

able pebbles may be formed of silicon carbide,

. 2 known. asthe pebble heating chamber. Pebble which pass downwardly through the heating chamber contact the rising combustion gas and are heated as above described. In apebble bed formed within such a chamber, as much as sixty percent by-volumepffthepebble bed issubstantially-static. For that reason fiue gases passing up through the static portion of the pebble bed leavethe top of the bed-at a relatively high tem. perature which results in a loss of considerable amounts of heat. Another disadvantage of such a pebble heater chamber is that most of the pebbles which are utilized in such a heat exchangeare quite brittle and fracture quite easily when dropped vertically onto a hard surface, such as the'top of the fluid pebble bed. withinthe pebble heater apparatus.

Anobject of this invention is to providemeans to substantially reduce pebblebreakage in'pebble heat exchangers. Another object of this invention is to rovide a method to substantially re duce pebblebreakage in pebbleheat exchangers. Another object of this invention is to provide means and a method to obtain more economic utilization of theheatexchange step within the upper chamber of pebbleheat exchangers. Another object of this invention is to reduce the amount of mechanical shock-to which pebbles are subjected in pebble heater chambers. Another object of this invention isto substantially elimiferredmodification ofthe invention. FigureBis abroken section elevation; of another modification of the invention. Figure 4 is a schematic view. of a pebble heater; apparatus. showing; the

relation betweenthe pebble heater and ugas heater chambers andthe path of pebble recycle.

Inthe deviceshown in-Figure l of the draw.- ing, pebble heater chamber II comprisesa shell 12 which is closed at its upper and lower ends by closure members '13 and M; respectively; Closure member 13 is providedin its upper end with apebble inlet. opening l5 preferably centrally positioned therein. Pebble outlet conduit 16 is provided in closure member IA. Shell l2. may be lined with insulating material. of. any type which will insulate the shell from thehigh temperatures to which pebbles within the chain-- ber are ordinarily subjected. A fluid mass of pebbles I1 is provldedwithin heater-chamber ll.

so as to form a contiguous pebble bed therein. A pebble flow control I8 is provided in pebble inlet opening I so as to prevent the pebbles from dropping vertically into the pebble heater chamber. inlet conduit I9 which extends downwardly through pebble inlet opening I5 to the top of the pebble bed within chamber II. Conduit I9 extends upwardly above closure member I3 for a considerable distance and is adjustably retained in position by adjusting member 2i which communicates with conduit member I9 by a pinion arrangement or some other suitable operative connection. Conduit member I9 is provided in one of its sides with at least one perforation 22 which provides communication between the interior of conduit l9 and pebble supply conduit 23. A helix is provided within pebble conduit I9 and extends from its lower end portion upwardly to and preferably extends above the perforate portion of conduit I9. Gaseous heat exchange material inlet conduits 25 are provided in the lower portion of chamber II and eliluent outlet conduit 26 is provided in the upper portion of chamber II.

In the operation of the device shown in Figure 1 of the drawing, pebbles are supplied through supply conduit 23 and pass laterally through perforation 22 into the interior of pebble inlet conduit I9. The iii-flowing pebbles pass onto the surface of helix 24 and pass downwardly through a circuitous route along the surface of the helix to the upper surface of the pebble bed within chamber II. Gaseous heat exchange material is injected into chamber Ii through inlet conduits 25. The heat exchange material may be in the form of combustion gases or may be passed into the pebble heating chamber in the form of combustible materials and burned therein in a combustion chamber provided therefor to form combustion gases. The combustion gases pass upwardly through the fluid pebble bed and gaseous effluent materials are removed from chamber II through efiluent outlet conduit 26. Heated pebbles are withdrawn from chamber 2 I through pebble outlet conduit I6. Conduit It may be raised or lowered by manipulation of adjusting member 2! so as to vary the depth of the pebble bed within chamber II as desired. Perforation 22 is of sufficient length to allow passage of pebbles therethrough regardlessof the positioning of conduit I9.

In a device shownin Figure 2 of the drawing, pebble heater chamber I I is somewhat similar to that shown in Figure 1 and comprises outer shell I2 which is closed at the upper end by closure member I3, which closure member is provided with a pebble inlet opening I5.- A fluid bed of pebbles Ii is provided within chamber II. Pebble flow control 28 comprises a pebble inlet conduit 29 which extends downwardly through pebble inlet opening I5. Pebble inlet conduit 29 is provided'in its upper end portion with an enlarged section SI which forms a pebble surge chamber therein. The lower portion of conduit 29 is formed by concentric cones 32 which are provided with perforations 33. Cones 32 provide an annular passage extending from the tubular section of conduit 29 downwardly and outwardly to the surface of the pebble bed adjacent the inner wall of chamber II. Lower cone 32 is affixed to and supported by support members, hotshown, extending between upper and lower cones 32. Pebble supply conduit 23 extends lat erally into the upper portion of enlarged conduit Pebble flow control I8 comprises a pebble 4 section BI. Effluent outlet conduit 26 is provided in the upper end portion of chamber II.

In the operation of the device shown in Figure 2 of the drawing, pebbles are supplied to pebble heater chamber I I through pebble supply conduit 23 downwardly and laterally into the enlarged conduit portion M of conduit Iii. A constantly replaced column of pebbles is formed within conduits iii, 29, and the annular conduit formed between cones 32 and extends downwardly to the upper surface of a pebble bed formed within chamber II. As pebbles are withdrawn from the bottom of chamber II, the pebble column within pebble inlet conduit 29 carries the incoming pebbles downwardly therethrough to the upper surface of the pebble bed. In that manner, vertical drop of pebbles flowing into the pebble heater chamber is substantially eliminated and considerable saving in material is effected by the reduction of breakage. Gaseous heat exchange material passing upwardly through chamber II is caused to pass through perforate cones 32 and through that portion of the pebble column within the annular conduit formed by the perforate r cones 32.

. In the device shown in Figure 3 of the drawing, chamber II is also somewhat similar to that shown in Figure 1 and comprises outer shell I2 which is provided in its upper end with closure member I3, which closure member is provided with pebble inlet opening IE and effluent outlet 23. A fluid bed of pebbles II is provided within chamber II. Pebble flow control 38 comprises pebble inlet conduit 39 extending downwardly through pebble inlet opening It and which conduit is replaceably afiixed in place by fastener means, such as threaded section l I. Pebble supply conduit 23 is provided with an enlarged section d2, which forms a pebble surge chamber therein, and is closed at its end adjacent pebble inlet conduit 39 so as to form an annular chamber about conduit 39. Conduit so is provided with perforations d3 within the closed portion of supply conduit 23, which perforations provide communication between supply conduit 23' and the interior of pebble inlet conduit 39. A constantly changing column of pebbles isprovided chamber II to a perforate section of conduit 39. Pebble supply conduit 23 is ordinarily maintained full'of pebbles at least a portion of the distance up and outward through enlarged coni duit section d2 therein. Pebble level gauge d4 extends slidably through the upper surface oi. enlarged conduit section 82. Pebble level gauge i l may comprise a float which may be raised or lowered by hand so as to determine the level of pebbles within enlarged conduit section 42. In that manner, it is possible to determine when additional pebbles should be added to the heater system. Effluent outlet conduit 25 is provided in the upper end portion of chamber I I.

In the operation of the device shown in Figure 3 of the drawing, pebbles are supplied through pebble supply conduit 23 and pass into enlarged portion d2 of the conduit without being subjected to a vertical drop therein. Aconstantly available pebble supply is thus provided for the pebble heater. The pebbles pass downwardly and laterally along conduit 23 through perforations 43 in pebble inlet conduit 39 and are carried downwardly to the upper surface of the pebble bed within chamber I I by a constantly replaced flowing column'of pebbles within pebble inlet conduit 39 as pebbles are withdrawn from the lower portion of chamber II. If it is desired to vary the depth of the pebble bed within chamber ll, pebble inlet conduit 39 may be removed and a pebble inlet conduit of a different length may be inserted and affixed in pebble inlet opening l5.

The device shown in Figure 1 or the modifications of Figure 2 or Figure 3 may be utilized in the pebble heater chamber of the pebble heater apparatus schematically shown in Figure 4 of the drawing. Pebbles are introduced into chamber l I through pebble supply conduit 23 and pebble inlet conduit 19. Gaseous heat exchange materials are admitted through conduit 25 and are caused to flow upwardly through the downwardly flowing mass of pebbles within chamber II and outwardly through eflluent outlet conduit 26. Pebbles are withdrawn through pebble outlet conduit l6 and flow downwardly into lower chamber 46 through which a, second gaseous heat exchange material which is to be heated is admitted into chamber 46 through inlet conduit 41 and is passed in a second heat exchange relation upwardly through the downwardly flowing mass of pebbles in chamber 46. Eiiiuent materials are removed from the upper portion of chamber 46 through eflluent outlet conduit 48 and pebbles are withdrawn from the lower portion of chamber 46 through pebble outlet conduit 49. The pebbles are then passed upwardly by means of elevator 45 to pebble supply conduit 23. Any conventional structure may be utilized for the introduction of gaseous heat exchange material into the pebble heater apparatus at the desired temperature. It should be noted that in the apparatus shown and described as Figure 4 of the drawing, the

' upper chamber of which may be chamber H of Figures 1, 2, or 3, a contiguous bed of pebbles is maintained from the upper port ion of pebble inlet conduits I9, 29, or 39, through pebble outlet conduit 49 in chamber 46 to elevator 45. Conduit 23 is preferably disposed at an angle slightly in is maintained from the upper portion of pebble utilized within the pebble heater apparatus. The pebbles are thus caused to roll through conduit 23 onto the pebbles within the pebble surge chamber or pebble conduit without encountering a point of vertical drop.

The method and device disclosed in connection with the modification of Figure 2 of the drawing are especially adaptable to the best utilization of heat input into the pebble heater chamber as well as eliminating the free drop of pebbles being introduced into the pebble heater chamber. The gaseous heat exchange material flows upwardly from the surface of the pebble bed, passes through the perforations in the cones 32 and downwardly flowing layers of pebbles formed between cones 32 and passes upwardlyand out of chamber [I through efiiuent outlet conduit 26. In this manner more contact between non-static pebbles and the hot effiuent gas is assured than would be possible with conventional pebble heater arrangements.

Though this invention is particularly applicable to the heating of pebbles for thermal conversion or similar thermal gas treating or heating processes, it is also adaptable to processes in which refrigeration of fluids is desired by heat exchange between pebbles cooled to a low temperature and gaseous heat exchange material.

As will be evident to those skilled in the art, various other modifications of this invention can be made or followed in the light of the disclosure and discussion without departing from the spirit or scope of such disclosure.

I claim:

1. A pebble heat exchange chamber which comprises in combination an upright closed. outer shell having a pebble outlet in its lower end portion; at least one upright pebble inlet conduit in formed thereby and extending from the lower end a of the conduit to the pebble inlet opening in said conduit; a heat exchange fluid inlet in the lower portion of said shell; and gaseous effluent outlet means in the upper portion of said shell.

2. A pebble heat exchange chamber which comprises in combination an upright closed outer shell having a pebble outlet in its lower end portion; an upright pebble inlet conduit having a pebble inlet opening in its upper portion, centrally positioned, closely fitted and slidably retained in and extending downwardly into the upper portion of said shell only to the desired pebble bed level therein; a drive member affixed on said shell and in operational communication with said pebble inlet conduit, adapted to vary the distance to which said pebble inlet conduit is extended into said shell; a helix within said upright pebble inlet conduit, said helix being closely encompassed by said pebble inlet conduit, and closing said conduit except for the: helical path formed thereby and extending from the lower end of said conduit to said pebble inlet opening in said conduit; a heat exchange fluid inlet in the lower portion of said shell; and gaseous efl'luent outlet means in the upper portion of said shell.

LOUIS J. WEBER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 1 Date 552,127 Howie Dec. 31, 1898 735,919 Tregidgo Aug. '11, 1903 745,689 Tanner et al Dec. 1, 1903 1,447,071 Giesecke Feb. 27, 1923 2,268,535 Schutte Dec. 30, 1941 2,399,450 Ramseyer Apr. 30, 1946 2,423,411 Simpson July 1, 1947 2,437,383 Dalton Mar. 9, 1948 2,439,372 Simpson Apr. 6', 1948 2,441,335 Sinclair May 11, 1948 2,443,337 Weber June 15, 1948 2,447,306 Bailey Aug. 17, 1948 2,451,924 Crowley Aug. 19, 1948 2,468,712 Kohler Apr. 26, 1949 FOREIGN PATENTS Number Country Date 154,510 Great Britain Dec. 2, 1920 

1. A PEBBLE HEAT EXCHANGE CHAMBER WHICH COMPRISES IN COMBINATION AN UPRIGHT CLOSED OUTLET SHELL HAVING A PEBBLE OUTLET IN ITS LOWER END PORTION; AT LEAST ONE UPRIGHT PEBBLE INLET CONDUIT IN THE UPPER END OF SAID CHAMBER AND FORMING THE SOLE PEBBLE INLET MEANS THERETO, EACH SAID INLET CONDUIT EXTENDING DOWNWARDLY INTO THE UPPER PORTION OF SHELL ONLY TO THE DESIRED PEBBLE BED LEVEL THEREIN AND EACH INLET CONDUIT HAVING AN INLET OPENING IN ITS UPPER PORTION; A HELIX WITHIN EACH SAID UPRIGHT PEBBLE INLET CONDUIT, CLOSLY ENCOMPASSED BY SAID PEBBLE INLET CONDUIT, CLOSING SAID CONDUIT EXCEPT FOR THE HELICAL PATH FORMED THEREBY AND EXTENDING FROM THE LOWER END OF THE CONDUIT TO THE PEBBLE INLET OPENING IN SAID CONDUIT; A HEAT EXCHANGE FLUID INLET IN THE LOWER PORTION OF SAID SHELL; AND GASEOUS EFFLUENT OUTLET MEANS IN THE UPPER PORTION OF SAID SHELL. 